In a magnetic disk device, a slider having a magnetic head flies at a location that is extremely close to a surface of the disk by using an airflow produced by rotation of a disk. By reducing the flying height of the magnetic head, it is possible to increase the sensibility of the magnetic head and prevent unnecessary spread of a magnetic field. Therefore, reduction in flying height of a magnetic head has been required to increase the capacity of a magnetic disk device.
Recently, the flying height of magnetic heads has been reduced by improvement in design of flying surfaces and by improvement in technology of processing sliders. Furthermore, a method of actively controlling the flying height has been proposed. For example, a resistor for heating is provided in a head and is supplied with a current to generate heat. The generated heat deforms the head so that a portion of the head protrudes toward a surface of a disk to thereby reduce the flying height. See Japanese laid-open patent publication No. 5-20635.
Meanwhile, recent concern has been raised that a space (flying height) between a head and a magnetic disk varies depending upon an air pressure. If the space is narrowed by variation of the air pressure, then the head may be brought into contact with the magnetic disk to produce dust (or contamination) or to cause wear of the head.
Accordingly, a conventional device has been required to have a wide space formed between a head and a magnetic disk in expectation of variations of the flying height due to an air pressure. Variations of the flying height due to an air pressure greatly differ from one head to another. Accordingly, read/write characteristics may be deteriorated in a case where a sufficient space is ensured between a head and a magnetic disk.
In this regard, the flying height may be controlled actively depending upon variations of an air pressure as disclosed in Japanese Laid-open Patent Publication No. 5-20635. However, a conventional magnetic disk device does not include a detector for detecting variations of an air pressure. Accordingly, the conventional magnetic disk device cannot employ such a proposed method. Furthermore, an air pressure sensor capable of detecting variations of an air pressure is considerably expensive. Therefore, if such an air pressure sensor is provided in a magnetic disk device, the cost of the magnetic disk device may problematically be increased. As disclosed in Japanese Laid-open Patent Publication No. 10-334626, a method of converting a servo current value into an air pressure may be employed to resolve the above problems. However, an air pressure has been desired to be measured more accurately for control of the flying height of magnetic heads.